More than anything, I think that is what happened in Charlottesville-most of the alt-right demonstrators were not from the area.
No, that wasn't the problem at all. Those protesters, wherever they were from, could have simply been allowed to peaceably assemble and air their views.
The "problem" was that violence-advocating thugs, armed with weapons and wearing masks, were bused in from all over the country to attack those protesters, and PREVENT them from exercising their free speech rights.
Of course this was encouraged and allowed as the police just stood and watched the attacks, rather than trying to protect the vastly outnumbered protesters from the "outside agitators."
This allowed them to claim that the situation couldn't be controlled so the whole protest march would have to be cancelled.